Electric oven for high temperatures working under vacuum or under neutral gas



Aug. 31, 1943.

F. MATHIEU 2,328,479 ELECTRIC OVEN FOR HIGH TEMPERATURE WORKING UNDER VACUUM OR UNDER NEUTRAL GAS Filed NOV. 22, 1941 Patented Aug. 31, 1943 2,328,479 ELECTRIC OVEN FOR HIGH TEMPERATURES WORKING NEUTRAL GAS UNDER VACUUM ORUNDER Francois Mathieu, Moissac, France; vested in the Alien Property Custodian Application November 22, 1941, Serial No. 420,120 7 Claims. (Cl. 13-8/) The present invention relates to a furnace for the production or recovery of certain metals and more particularly to an electric furnace for carrying out thermal reductions in a vacuum or in a neutral gas for the production or recovery of cern tain metals.

The recovery of certain metals, and particularly magnesium, by thermal reduction is known and produces certain metals, including magnesium, of a high state of purity. However, diillculties encountered in the use of furnaces for this process, which are capable of long use, the latter being a factor indispensable in the obtaining of a low net cost, have retarded the popuiarization of the process. Heretofore it has been necessary to use furnaces of thick metal, or furnaces of ma sonry without strength and air tightness.

The present invention has for one object the avoidance of the aforesaid diillculties and resides in a readily constructable and inexpensive furnace, which may be used in every case where' it is desired to carry out a thermal reduction or like process in a vacuum or in the presence of a neutrai gas at elevated temperatures, as for example, from 1300o to 1600 C. The furnace according to the present invention makes possible the recov ery,- by condensation in the form of crystals, a higher percentage of metal from the heating of substances for reaction, and particularly so when used for the production of magnesium. The furnace makes possible also the purification of this and other metals.

In carrying out one form of the invention, the walls of the heating chamber are made of magnesia brick covered on the outside with a compressible insulating material, which prevents the transmission of heat and the counter pressure to the Walls of the frame, which is disposed about the insulating material. Thus the walls of the heating chamber are subjected to the same internal and external pressure and do not require high mechanical'strength at the expense of resistance to heat. For this reason it is ypossible to make the walls in the heating chamber of a material highly resistant to high temperatures, thus assuring them a prolonged usage. The condenser on which the metals recovered are condensed is disposed in a passageway communicating with the heating chamber and the matter to be condensed is directed into contiguity withvthe condenser, so as to provide for a maximum recovery of metal.

Accordingly, an object of the invention is to provide a furnace of high refractory characteristics.

Another object of the invention is to provide a condensing member for a. furnace of the character described disposed in a passage at one side Lof the heating chamber in combination with means for directing matter to be condensed into contiguity with the condenser.

Still another object of the invention is to dispose the condensing member in a passage at one side of the heating chamber, the condensing member being supported from the outer door to the passage and being protected against direct radiation from the source of heat within the heating chamber.

A further Object of the invention is to provide a furnace having a condenser therein shielded against direct radiation from the source of heat within the furnace.

A still further object of the invention is to provide a furnace having a condenser therein and means to direct matter to be condensed into contiguity with the condenser.

These and other objects will be apparent from the following specification when taken with the accompanying drawing. in which Fig. 1 is a diagrammatic longitudinal section of a furnace according to one Way of carrying out the present invention,

Fig. 2 is a section along the line II-II of Fig. 1, and

Fig. 3 is a diagrammatic vertical section of an alternate form of condenser.

Referring particularly to Figs. 1 and 2, the reference character I indicates a framework or housing, which preferably, although not necessarily, is oi.' cylindrical form. Disposed within the framework I is a heating chamber 5, having a, lining 3, preferably constructed of magnesiol bricks, although it is to be understood that any suitable refractory may be used. The lining 3 also may be cylindrical although this shape is not essential. Disposed between the framework I and the lining 3 of the heating chamber 5 is a. mass of compressible insulating material 2. The lining 3 may be supported adjacent the lower side ythereof from the framework I by suitable supporting members, or it may be supported directly by the insulating material 2 as desired.

Disposed in one side of the heating chamber 5 is a charging passage 4 defined by a tubular member 1, generally in the form'of a truncated cone. The member 'l is surrounded by the compresslble insulating material 2., which in turn is surrounded by a portion of the framework I. At the outer end of the member 1 is a hollow annular ring I2, I2* for the having suitable connections I21 and circulation of a cooling liquid such as water. 'I'he ring I2 forms a continuation of the member l and of the passage 4. `At the outer end of ring I2 is a removable door or gate III, which is secured to the ring I2 by suitable screws II. It will be understood that the door I I! is the door to the heating chamber 5. While,`as shown, the ring I 2 is not outwardly diver-ging, continuing the outward divergence of the member 1, it is to be understood that the ring I2 may be outwardly diverging if desired. However, in the `claims it is contemplated that the expression outwardly diverging applies to passage 4 whether it is outwardly di verging throughout its entire length or only a part thereof.

Secured to the door I is a tubular member I 3 supporting a condenser I in the form of a hollow cylindrical member. The tubular member I3 is arranged with an internal tube |31 and inlet and outlet connections I32 and I33 respectively for providing for the circulation of cooling liquid through the condenser I5. The tubular member I3 is connected to the door III by nuts I41 and I42 on opposite sides thereof, whereby the distance of the heating chamber 5 may be reguated so as to place the condenser in the zone of condensation most favorable to the substance treated.

Supported on the tubular member I3, between the condenser I5 and the door III, are a plurality of bailles I6 extending into contiguity with the tubular member 1. It will be observed that since the condenser I5 is within the tubular member l, the tubular member 1 serves to conduct metallic vapors from the heating chamber 5 towards the condenser I5. At the same time the baliies I6 prevent the passage of metallic vapors past the condenser where they would condense on the door I I)v and the cooled ring I2.

Within the heating chamber 5 is provided a container 6, which is preferably tubular in form for, lsupporting the substances for reaction I9. One end of the container 6 is open, and the open end is disposed within the passage 4 sov that metallic vapors from the substances for reaction will be directed into contiguity with the con.- denser I5 by the walls of the container 6 as well as by the member l.

Projecting into the heating chamber 5 are three pairs of electrodes 41, 42 and 43 respectively, having suitable connections with a source of electric power which arcs across the respective pairs of electrodes to generate heat. It is preferred that each pair of electrodes be connected to a transformer having a variable output so that the heat may be varied to maintain a uniform temf perature in the chamber 5. Also it 'is preferred that the electrodes be replaceable independently of the replacing of the lining 3.

For drawing a vacuum in the heating chamber 5 and passage 4 there is provided a tube I8 communicating with the passage 4 between the door I0 and the condenser I5. The tube I8 may be connected to some suitable vacuum pump not shown. The drawing of a vacuum from a position between the door I0 and the condenser I5 not only conveniently exhausts the interior of the heating chamber 5 and the passage 4, but it .also tends to direct metal vapor from the container 6 into contiguty with the condenser I5.

In Fig. 3 is disclosed an alternativeiorm of condenser I1 which is' supported on a tubular member I3 like that provided for the condenser I5 as disclosed in Fig. 1. The condenser Il is on the outer end of the tubular member I3 and is behind the condenser Il are baiiles I6 identical with the baiiles I5 associated with the condenser I5 of Fig. 1.

The operation of the furnace is as follows:

The container 5 containing substance for reaction I9 is disposed on the floor 8 of the heating chamber 5, having been inserted through the charging passage 4. The door I0 is then closed and secured by the suitable screws II. Previously to closing the door I0, however, the relative longitudinal'positlon of the condenser I5 in the charging passage 4 is regulated by manipulation of the nuts I41 and I4.

When the door I Il has been properly secured in place the circulation of water or other cooling liquid through the ring I2 and the condenser I5 is started, and the vacuum pump not shown is started to exhaust the interior of the heating chamber 5 and the passage 4 through the tube I8. The framework I preferably is of metal, all sections thereof being either welded or otherwise secured into a sealed unit so that when the door I0 is secured the atmospheric pressure is resisted by theframework I and the door |II. Since there will besome leakage between the lining 3 and the space between the lining 3 and the framework I, the pressure on both sides of the lining I will be equalized so that the drawing of a vacuum within the heating chamber 5 and passage 4 will not place any additional stress on the lining I'. Also the compressibility of the insulation 2 prevents any stress on the lining 3 from expansion thereof that might otherwise result from the resistance of the framework I. As soon as the vacuum has been created the electric power is connected to the electrodes 41, 42 and 43 to heat the heating chamber 5.

Under the action of the heat the substance for reaction I9 in the container 6 gives oil a metallic vapor which is directed by the container 5 and `operation again ,by reloading the member 'I into contiguity with the condenser VI5 where it condenses and forms a mass of metal |52. In Fig. 3 the condensed metal is indicated by the reference character I'Il and in Fig. 4 the condensed metal is represented by the reference character 202. 'The bailles I 6 prevent the passage of metal vapor therepast to prevent it from condensing on the ring I2 and the door Il.

As soon as the operation has been nnished and the vacuum pump is stopped, the door I5 Is opened and the tubular member I3 together with the condenser I5 are withdrawn to remove the metallic vcrystals which have settled on the condenser I5. The furnace may be put back into the container 5 placing the same 8 of the heating chamber 5 and a second condenser in the passage the same condenser in the passage condensed metal has been removed with substance for reaction I9. on the floor either placing 4 or placing 4 after the therefrom.

The present invention has particular adaptability for rduction processes. However, it il not intended that the structure be limited to any particular use as it may be employed wherever desired. The condensing member is conveniently located in the charging passage 4. However, it will be appreciated that equivalent arrangements within the scope of the attached claims may be employed with equally desirable results. Furthermore, while the container t for conven- Disposed i ience is open ended, it will be readily apparent that the entire end of the container 6 need not be open. When carrying out a process in the furnace according to the present invention in a neutral gaseous atmosphere, the neutral gaseous atmosphere may be obtained in any known manner.

Having thus described my invention what I desire to secure by Letters Patent and claim is:

1. A furnace of the character described comprising a heating chamber, a passage having one end communicating with said chamber, said passage having a removable door on the other end thereof, said passage being substantially vunl'- formly outwardly diverging, a condensing member disposed in said passage and supported by said door, and defiecting means within said chamber to direct matter to be condensed from said chamber into contiguity with said condensing member, said passage being relatively small in transverse cross-section with respect to the size of said condenser.

2. A furnace of the character described comprising a heating chamber, a passage having one end communicating with said chamber, said passage having a removable door on the other end thereof, a condensing member disposed in said passage and supported by said door, said passage being substantially uniformly outwardly diverging, and a substantially closed container within said chamber for supporting matter for reaction, said container having 'an opening at one end thereof for directing matter to be condensed from said container into contiguity with said condensing member, said end of said container being disposed in said passage, said passage being relatively small in transverse cross-section with respect to the size of said condenser.

3. A furnace of the character described comprising a heating chamber, a passage having one end communicating with said chamber, said passage having a removable door on the other end thereof, said passage being substantially uniformly outwardly diverging, a condensing member disposed in said passage and supported by said door, and a tubular container within said chamber for supporting matter for reaction, said container having an opening at one end thereof, said end ci said container being disposed within said passage for directing matter to be condensed from said container into contiguity with said condensing member, sai-d passage being relatively small in transverse cross-section with respect to the size of said condenser.

4. A furnace of the character described comprising a heating chamber, a source of heat in said chamber, a passage having one end communicating with said chamber, said passage having a removable door on the other end thereof, a condensing member disposed in said passage and supported by said door, said passage being substantially uniformly outwardly diverging, and a substantially closed container within said chamber for supporting matter for reaction, said container having an opening at one end thereof for directing matter to be condensed from said container into contiguity with said condensing member, said endof said container being disposed in said passage, said condenser being shielded from direct radiation from said source of heat, said passage being relatively small in transverse cross-section with respect to the size of said condenser.

5. A furnace of the character described cornprising a heating chamber, a source of heat within said chamber, a passage having one end communicating with said chamber, said passage having a removable door on the other end thereof, a condensing member disposed in said passage vand supported by Said door, said passage being outwardly diverglng, a substantially closed container within said chamber for supporting matter for reaction, said container having an opening at one end thereof for directing matter to,

be condensed from said container into contiguity with said condensing member, said end of said container being disposed in said passage, and a plurality of baiiiing plates associated with said condensing member extending substantially across said passage into contiguity with the Walls of said passage between ber and said door for restraining the passage therepast of matter to be condensed, said condenser being shielded frorn direct radiation from said source of heat.

6. A condensing member of the character described comprising an internally liquid cooled condensing surface, a support for said surface, and a plurality of battling plates secured to said support behind said surface. Y

A furnace of the character described comprising a heating chamber, a source of heat within said chamber, a passage having one end communicating with said chamber, said passage having a removable door on the other end thereof, a condensing member disposed in said passage and supported by said door, a substantially closed container within said chamber for supporting matter for reaction, said container having an opening at one end thereof for directing matter to be condensed from said container into contiguity with said condensing member, said end of said container being disposed in said passage, and a. plurality of baffling plates associated with said condensing member extending substantially across said passage into oontiguity with the walls of said passage between said condensing Amember and said door for restraining the passage therepast of matter to be condensed, said condenser being shielded from direct radiation from said source of heat.

FRANCOIS MATHIEU.

said condensing mem- 

